Process of bleaching oils



yMarch 8, 1938. la.l CLAYTON ET AL APROCESS oF BLEACHING ons Filed June28, 193'/ Patented Maa-'8, i938 UNITED STATES.

PROCESS BLEACRING OILS Benjamin clama, nousmn,.rex., alla Benjamin Il.Thurman, Bronxville, N. Y,

' Application June 2.8, 1937, Serial ldd-150,824

' 9 claims.

Crude glyceride oils, such as animal, vegetable anddish oils, usuallycontain various impurities, l for example, fatty acids, coloring matter,and gums. The fatty acids and gums can be almost completely removed byrefining processesemploying caustic soda or other alkaline refiningagents.

lSuch reilning processes ordinarily includeyth'e mixing of properproportions o f a caustic soda solution with the loil so that alkalireacts with the free fatty acldsto form soap and the separation of theAresultant soapfrom the oil. Most of the-gums present separate with thesoap and if the refining process is properly conducted a large part ofthe coloring matter is likewise lseparated with the soap. The refiningprocess may be continuous or batch and the' soap, along with otherimpurities, separated from the reiined oil by vcentrifugal separation'-or settling.

usually contains small amounts of soap, water, and free alkali. If thesoap and free .alkali are present in appreciable quantities they can beremoved by washing with water, as by mixing water with 4the oil eitherin abatch or continuous process and. then separating the water in whichthealkali and soap are dissolved by either a centrifugal or settlingoperation. 1

In many instances the reilning operation leaves the oil, too highlycolored -for an acceptable commercial product and it has been thepractice in the art to treat this oil With/a bleaching agent .as bymixing such bleaching agents as fullers earth, acid treated clay or nelydivided carbon with the oil and then filtering the bleaching agent 4fromthe oil. 'I'his method of bleaching or removing ythe nal colorisexpensive as large filter presses and large quantities of bleachingagents are required. Also a considerable .proportion of the oil is lostby being retained in the bleaching agent andv discarded therewith.The\present in-l vention provides a process which may be employedin lieuof the conventional processes emplaying bleaching agents or in case theoil is extremely highly colored, it may be employed in addition totreatment with'bleaching agents. In .the latter 'case both the amountoi' bleaching agent and the amount'ofv oil lost in the process laremarkedly reduced. n 4

The reiined oil from the above described processv Bassum l Also, inaddition to the impurities discussed above, glyceride oils, in manycases, contain volaltile and other impurities which are no t removed bythe above described r'e'ning process or in the washing and bleachingsteps of the prior art. 5 Certain of these impurities. give theresultant oil an objectionable odor and ilavor or deleteriously aifectthe keeping qualities or the oil. These impurities can be removed byvaporization in thepresent process or broken down into other coml0pounds, which are not objectionable by the temperatures employed. Thus,the oil may be deodorized and improved in flavor and keeping qualities,as well as bleached, by the present invention. If a crude oil isrelatively pure or the l5 nature of its intended use does not require ahighly refined oil, the present invention may be applied tosuch a crudeoil to reduce its color and remove other objectionable impurities, butthe invention findsA its greatest utility in bleaching 20 previouslyrefined oils. 7

It is, therefore, an object ofthe present invention to provide animproved process of bleaching glyceride oils.v l

Another object of the invention is to provide 25 an improved process ofbleaching previously refined glyceride oils. 1

Another object of the invention is to provide an' improved process ofbleaching glyceride oils in which no bleaching agents are required.

A further object of the invention is lto provide a. continuous processof bleaching glyceridev oils in which the oil is subjected to elevatedtemperatures out of contact with the air and cooled before being broughtagain in contactwith the air.

A still further object of the invention is toprovide an improved processof bleaching glyceride voils and at the same time removing vaporlzableand other impurities. y

In` accordance with the present invention, the 40 glyceride oil ispassed continuously through a heating zone where itstemperature-isfrapidly raised 'and wherein it is maintained out ofcontact with the atmosphere. The temperatures contemplated ,by thepresent invention are, in general sumciently high that contact with theatmosphere by the heated oil would cause deterioration of the oil. Whenthe desired temperature of the oil has been reached, the oil is quicklycooled to a -temperature at which it will not be deleteriously ailectedby contact with the atmosphere by being passed through a cooling zonebefore it is discharged into contact with the atmosphere, f

The temperatures to which the oil is subjected cannot be preciselystated since they will vary with the type of oil being treated and theamount of bleaching necessary for a particular oil. For

a linseed oil or soya bean oil this temperature may reach 500 to 600 F.while for cottonseed, corn, sesame or other of the more edible oils,temperatures between 420 and 500 F. are usually sufficient. If a slightbleaching only is required, it will be apparent that the temperature towhich a -given oil is subjected may be somewhat lower.

The bleaching of the oil .appears to be a function of the temperaturereached and it is not necessary to maintainl the oil at the high tem;perature over a period of time. If the oil is4 maintained at such hightemperature for an extended period of time, polymerization, as well ascracking, may occur with an increase of fatty acid content and theproduction of an undesirable flavor and darkening of the oil so thatsatisfactory bleaching. is not accomplished. It is, therefore, desirableto heat the oil as rapidly as possible and then cool the oil .as rapidlyas possible.

The pressure in the heating zone will ordinarily be onlythat-necessaryto force the oil through the zone since 'high pressure isnot necessary for the present bleaching process and it is furthermorenot necessary to prevent vaporization of 'all of the more volatileconstituents pressure than theheating zone-and in some instances theemployment of a vacuum chamber is found to be desirable. Even ifvaporization has been allowed to occur in the heating zone, dischargingthe heated oil into a lower pressure or vacuum chamber will causefurther vaporization of volatiles and expansion of those already formedso as to cool the oil. With certain oils it has been found that a betterbleach is produced by entirely preventing vaporization in the heatingzone while with other'oils it has been fou`nd desirabletoemploy asuiiiciently low pressure in the heating zone to provide forvaporization therein. Aside from the cooling effect of vaporization'incooling the oil after it is discharged from the heating zone, a portionof the coloring matter appears to be removed with the l vapor -alongwith other vaporizable impurities contained in oil so that it is-desirable to withdraw vapors from the oil while it is in a heatedcondition or during cooling thereof. urated or superheated steam may beintroduced into the expansion 'chamber to assist in the vaporization ofthe volatilesA and with certain oils it has been found that a betterbleach is proa duced by the presence ofY small proportions of Waterinthe oil when it is introduced into the heating zone. remaining in theoil after the oil has been refined or after being washed as abovedescribed, oradditional Water may be introducedinto the oil before it isheated. Thus, with cerating oils the present process may also Operate todry the Either sat- This water may either be that oils and it isunnecessary to employ a separate drying step. With other oils it hasbeenfound desirable to heat them in the absence of moisture in whichcase a dry oil is employed or the oil is dried before it is heated.

The oil may be further cooled before discharg- Ving the same to theatmosphere by being passed in heat exchange relation with alcoolingmedium either in the expansion chamber orin an additional chamber sothat the temperature of the oil is below that at which oxidation orother deleterious action occurs when it is again contacted with theatmosphere.

A diagrammatic drawing of an apparatus suitable for carrying out thepresent process is shown in the single figure of *the attached drawingand the process will be described in more detail in connectiontherewith.

Referring more particularly to the drawing, I indicates a tank forreceiving the oil to be bleached, which oil ma be either a crude oil ora previously refined oi As stated above, this oil may be either dry ormay contain small portions of water depending upon the type of oil beingtreated. The oil is withdrawn from tank `I through a pipe 2 in which ispositioned a control valve 3 and is forced by a pump 4 through a pipe 5connected to the .inlet of a heating coil 1 positioned in a heatercasing 8. The oil leav- II secured to lthe closed endl'I2 of the hollowmember I0. The other end I3 of the tube II is open landis slitted andspread so that the ends of the spread portions contact with the 'insidesurface of the hollow member III leaving openings for the'oil to passthrough the tube II into an annular space Il between the tube Illand theinterior surface of the hollow member I0. The oil is vdischarged fromthe hollow member I through pipe`I which leads from the heat regulator 9to the exterior of the heater casing 2.

One end of' the .heat regulator 9 is held in adjusted position by thethread support I 6 passing through a correspondingly threaded opening inthe wall of the heater casing 8. A hand wheel II i's provided at theouter end of the support I6 and tlie interior end of the support I6terminates in an enlargement `-I8 rotatable in a recess I9 providedtherefor in the closed end I2 of the hollow member IU. By turning thehand wheel I'I lthe heat regulator 9 can be moved lon- -Igitudinally toadjust the temperature i' the oil leaving the heating oil 1 as will behereinafter described.

The end of the hollow member IB opposite the support I6 is provided witha stem or extension which extends through van opening 2| in the wall ofthe heater casing- 8. VA fuel valve 22 is xed on the outer end of thestem 20 and is positioned in the Valve housing 23 attached to the wallof the heater casing 8. The valve housing l amount of fuel delivered tothe heater is controlled by the valve 22 and the controlled amount offuel is conducted by a pipe 21 to a burner 28 positioned below the heatregulator or thermostat assembly 9 so that products of combustion Immthe burner. 28 contact with both the heat perature of the hollow memberI0. and therefore the amount of fuel fed to the burner 28 def pends bothupon the temperature of the products of-combustion and the temperatureof the oil leaving the 4coil 1. It has been found `thfat thisarrangement automatically maintains an extremely uniform dischargetemperature of the oil leaving the coil 1 and that this uniformdischarge temperature may be predetermined., by

adjustment of the hand wheel I1. Also in case of failure of the oilsupply to coil 1, the hollow member I9 is rapidly heated to shut offsupply Y o! fuel before damage vdue to high temperature occurs to theheater casing 9 `or the elements enclosed therein@ Pipe I5 delivers theoil Vdischarged from the heat regulator. 9 to an evaporating orexpansion chamber 29 and terminates thereinvin a discharge nozzle 30. Avalve 3l may be positioned in the pipe I5 so that anydesired pressure intheheating coil may be imposed by the pump 4 and main- -tained bypartially closing this valve.. Alternatively the nozzle 30 may be, madereplaceable so that nozzles having .diil'erent sized ldischarge openingsmay be substituted to maintain theden sired pressure or the diameter ofthe pipe 1 of the coil may be made sufficiently small so that thedesired pressure is maintained without the necessity of a restricteddischarge. Af steam supplypipe 32 may be providedfor introducing 'eithersaturated or superheated steam into the expansion chamber 29 to assistinva orization or add additional heat in the pansion chamber 29. Vaporsare withdrawn Ifr m the expansion chamber 29 by a pipe 3 g to acondenser 34. 'I'he condenser may be of any suitable type and mayinclude a cooling coil 35 connected to pipe 33 and positioned ina casing34, through which a cooling medium may be circulated. The vcondensercoil 35 maydischarge into a receiver 31 to 'which a vacuum pump 38 ist,vconnected by a pipe 39. "If evaporation and con densationat atmosphericpressure is desired, the receiver 31 may be vented directly to theatmosphere by opening the valve 40 in the pipe 4I. Condensate may berembved from the receiver 31 through a pipey 42 and a pump (not shown)may be employed for this purpose, when a vacuum is maintained inreceiver 31,A

` A valved dischargepipe 43 leads from the bottom of the expansionchamber 29 and is con- 'vice 46 which may include nected to a pump 44for withdrawing the treated oil'from the expansion chamber anddischarging the same through a pipe 45 to a cooling del la coil 41positioned in a chamber 4 t hrough which a cooling medium may be passed.An'eective manner of conserv- `ing heat in the process is to employ theoil being delivered tothe heating coil 1 as a cooling medium for coolingthe oil inthe expansion chamber 29. 'I'his `can lbe accomplished whenhigh temperatures in the expansion chamber are not required by owing allorjaportion of the oil entering the process through the pipe 50 providedwith a` valve 5I and connected to the pipe 2 between the tank I andthevalve 3 and then through a cooling coilv 52 positioned in theexp'ansion` chamber 429 and returning the oil through a pipe 53 andvalvev54 to the pipe 2 bel tween the. valve 3 and the pump 4. By closingor partially closing the valve 3 and opening or partially opening thevalves 5I and 54 any desired portion of the oil from the tank I can berun through the cooling coil 52 so as to preliminarily heat the oilentering the. coil 1 and cool the oil in the expansion chamber 29.

'I'he rate at which the oil is passed throughthe coil 1 as well as theamount of heat applied to the coil will usually'bediil'erent fordiierent oils being treated since the temperatures suitable for diierentoils will vary as above discussed. By setting the hand wheel I1, thedischarge temperature of the oil is maintained substantially 'f constantby the automatic neatrgulator s at any desired temperature. Itis, ofcourse, understood that any other means of. rapidly heating the oil suchas a steam or liquid heating bath may be employed instead of usingproducts of combustion directly in contact with the heating coil. Bythis invention, glyceride oils aretreated-in such a way that theyarebleached very eifectively and eiiiciently and in an economicalmanner. It requires only a very few minutes, for example, four to tenminutes, to increase the `temperature of the il from room temperature orthe temperature atwhich it is discharged from the previous refining orother steps to the tem-- pera'ture required to bleach the oil. Thisshort time of heating and the fact that the oil is maintained out ofcontact with the atmosphere while it is in a highly heated conditionprevent injuring the oil. Also thefvelocity ot the oil through the tircoil 1 is such that substantially uniform heating a specific example ofthe present invention, a

previously refined cottonseed oil having an original colqrpf 37 yellow,'I red was bleached in a -few minutes to a color of 30 yellow, 3 redwithout employing any bleaching agents, l By testing samples of the oilto be treated, the art can readily ascertain whether to heat t'heoil ina dry condition or with small proportions of water and also thenecessary temperature reached in the heating coii. With extremelydiiiicult oils to bleach, the present process may be preceded-- orfollowedby a conventional bleaching stepv employing bleaching agentssuchas fullers earth or carbon. However, even in such casca-the loss fof oil as well as the amount of bleaching agent required is markedlyreduced by employing the present invention Aas a part of thebleachingoperation. Volatile impurities are removed by expanding the heated oilinto the closed chamber 29.' Such volatile impurities can be condensedand,collected in the receiver 31 and in many cases constitute valuableby-products. When it is not desired to operate the expansion chamber291m'- der vacuum conditions or t recover the volatile impurities thecondenser 34 and receiver 31 can `be omitted.' l'

Although the present invention has particular utility inbleachingglyeeride oils 'which have 'been previously refined there arecertain glyceride oils whichybecauseof the nature of their use ora theirexcellent quality in a crude state, do not require refining-butnevertheless should have their color reduced. The present invention 20animal 'a is applicable to such oils ev n though they have not beenpreviously refined. nd is effective to reduce the color thereof. Noreagents such asalkali or bleaching agents are required and the oil 5 issubjected merely to heating and cooling out of ,contact with theatmosphere. For example, linseed oil which has been cold pressed andwhich has not been neutralized and refined with alkali aswell as linseedoils which have been refined v may be bleache'd to colors of 20 yellow,2 red or less.

Although we have described the preferred embodiment of our invention, itis to beunderstood that thepresent invention is not to be limited to theprecise details of the process herein disclosed but may be varied withinthe scope of the following claims.

What w claim is:

1. 'I'he process of bleaching previously refined v'e'getable oils whichare substantially free of free fatty acids, which comprises, passingsaid oils under pressure and out of 'contact with the air through .aheated zone of such dimensions that the oil is substantially uniformlyheated, raising the temperature of said oil in said zone sufficient toreduce the color of said oil and cause volatile constituents to passinto vapor when' th pressure is lowered, cooling said oil before theviscosity characteristics thereof have been materially changed bysuddenly lowering the pressure and withdrawing said volatileconstituents. n. 2. The process of bleaching previously refined animaland vegetable oils which are substantially free of free fatty acids,which comprises, passing said oils at an elevatedpressure and out ofcontact with the air through a heated zone of such dimensions that theoil is substantially uniformly heated, raising the temperature of saidoil in said zone suicient to reduce the color of said oil and causevolatile constituents to pass into vapor when the pressure is released,cooling said oil before the viscosity characteristics thereof have beenmaterially changed by suddenly releasing said pressure and withdrawingsaid volatile con-Y stituents and further cooling said oil beforebringing the same into contact withthe air. 3. 'I'he process ofbleaching previously refined aniral and vegetable oils which aresubstantially free of free fattyfacids, which comprises, passing saidoils under pressure through a heated zone and out of contact with theair, maintaining suicient velocityof vsaid oil in said )zone to causethe oil to be substantially uni- 65. formly heated-raising thetemperature of the oil in said zone sufcient to reduce the'color of saidoil and cause volatile constituents thereofto ,pass into vapor when thepressure is reduced, sud'den- :y releasing saidA pressure to cool saidoil 'before the viscosity characteristics of said oil have beenmaterially changed by delivering the oil Vinto a lower pressure zone andwithdrawing said volatile constituents. f

4. The process .of bleaching previously refined g5 animal and vegetableoils which are substantially free of free fatty acids, which comprises,passing said oils at an elevated pressure and out of contact with theair through a'heated zoneo'f such dimensions that the oil issubstantially unifam- 7`0 ly heated, raising the temperature of 4saidoil in said zone to approximately .500 F., cooling said oil before theviscosity characteristics thereof have beenmaterially changed bysuddenly'releasing the pressure and withdrawing volatile 16' productstherefrom.

.5. VThe process -of bleaching previously refined animal and vegetableoils which are substantially free of free `fatty acids, which comprises,passing said oils through an elongated 'curved heated zone at atemperature sufficient to reduce der pressure and out of contact withthe air through a heated zone of such dimensions that the oil issubstantially uniformly heated, raising the temperature of said oil insaid zone suflicient to reduce the color of said oil and cause volatileimpurities to pass into vapor when the pressure 'is lowered, coolingsaid oil before the viscosity lcharacteristics thereof have beenmaterially changed by suddenly lowering the pressure and withdrawingsaid volatile impurities.

'1. The process of bleaching previously refined -glyceride voils whichare substantially free of free fatty acids and removing volatileimpm'ities therefrom, which comprises, passing said oils under pressureand out of contact with the air through a heated zone of such dimensionsthat the oil is substantially uniformly heated, raising the temperatureof said oil in said zone suflicient to reduce the color of said oil andcausev volatile impurities to pass into vapor when the pressure islowered, cooling said oil before the viscosity charactertistics thereofhave been materially changed by suddenly discharging said oil into avacuum zone and withdrawing said volatile impurities from said vacuum.

8. The process ofv bleaching previously refined glyceride oilswhich 'aresubstantially free of free fatty acids and removing volatile impuritiestherefrom and recovering the same, which comprises, passing said "oilsunder pressure and out of contact with the air through a heated zone ofsuch dimensions that the oil'is substantially uniformly heated, raisingtheV temperature of said oil in said zone sumcient to reducethe color ofsaid oil and cause volatile impurities to 'pass vinto vapor when thepressure is lowered, cooling said oil before the viscositycharacteristics thereof have been materially changed by suddenlylowering the pressure and withdrawing said volatile impurities 'andcondensing the same. f.

9. The process of bleaching previously refine glyceride oils which aresubstantially free of free fatty acids, which comprises, passing saidoils containing a small, proportion of'water under pressure and out ofcontact with the air through a heated zone of such dimensions that theoil is substantially uniformly heated, raising the temperature of Saidoil in said zone sufficient to reduce the color of .said oil and causevolatile 1 constituents, including said water, to pass into y vapor whenthe pressure is'lowered, cooling said oil before the viscositycharacteristics thereof 'havebeen materially changed by! suddenly low-,ering the pressure and withdrawing said volatile constituents.

v BENJAMIN'- CLAYTQN- BENJAMIN H.

